It is known from civil engineering physics that in buildings, sufficient footfall sound insulation of partition components andxe2x80x94at the same timexe2x80x94a realistic mass of these components can only be attained with multi-shell components (double-shell components, as a rule) or with a combination of heavy single-shell partition ceilings and softly resilient wear surfaces. Double-shell partition ceilings generally are realized as floating floor screeds, and thus as a rule give rise to relatively thick designs which especially in the renovation of old buildings having predetermined joining heights can hardly be installed in practice. When calculating the footfall sound improvement factor (FSIreq) of multi-shell ceiling covers that is required for the minimum footfall sound insulation of the full structure, not all European countries allow softly resilient wear surfaces to be taken into account. Moreover, such surfaces sometimes are not acceptable or not suitable, particularly so in wet areas (bathrooms).
In recent times, to the contrary, floor and wall coverings which are relatively thin and rigid are increasingly applied, for instance coverings consisting of chipboards or presspan panels in boarding sizes which have extremely hard surfaces, such as laminated plastic. The properties of these floor and wall coverings, which act as single-shell structures, are subjectively unpleasant and critical particularly with respect to footfall sound projection.
In Germany and Austria, floating floor screeds are the technical standard in footfall sound insulation. However, floor coverings cannot be included when technically demonstrating that minimum footfall sound insulation is attained, since they are subject to aging and can be exchanged. The resonant frequency of softly resilient wear surfaces decreases with increasing contact time; this in turn depends on the depth of penetration of the sound-generating object into the surfacing, and this depth in turn will of course be a function of the dimensions and mass of the footfall sound generator. This correlation also constitutes the reason why the results obtained when measuring the sound level reduction by wear surfaces with the aid of a standardized hammer mill basically differ from those obtained when walking on the same partition ceiling structure.
In building practice, thin, rigid wear surfaces can be installed as floating structures when they can guarantee a sufficient load distribution, and thus could basically constitute a solution intermediate between a floating floor screed and a softly resilient wear surface. Today, however, most of these wear surfaces still have the disadvantage with respect to footfall sound insulation that
on one hand the mass of the load-distributing layer generally is relatively small, and hence the dynamic stiffness of the intermediate layer must be distinctly below 10 MN/m3 in order to attain an acceptable footfall sound improvement factor for the double-shell structure, but traditional footfall sound-proofing materials can provide such an improvement only when used in rather large layer thicknesses resulting, in their turn, in large overall thicknesses of the structure.
on the other hand the footfall sound properties of the rigid, single-shell wear surface itself are extremely unsatisfactory because of its usually very hard top layer, the associated small depth of penetration of the footfall sound generator (short contact times), and the resulting unfavorable resonant frequency, which can even be felt in a subjective way. Often this becomes noticeable as well in the form of unpleasant walking noise (xe2x80x9crattlexe2x80x9d) in the room.
The standard DIN 4109 that is applicable when technically demonstrating the sound reduction factor provides examples of ceiling covers that will attenuate footfall sound. For instance, a footfall sound improvement factor of as much as 25 dB can be expected for wooden sub-floors consisting of chipboard panels with a minimum thickness of 22 mm installed so as to be floating over their full surface area on fibrous insulating materials having a dynamic stiffness sxe2x80x2 of at most 10 MN/m3. It can already be seen from this example, however, that special precautions will be required in order to attain improvement factors of the same order of magnitude with distinctly thinner floor coverings, such as wood or laminate flooring.
It has been the task of the invention, therefore, to provide a composite sound insulation system that improves, both the footfall sound insulation and the room acoustics, and this particularly when using thin, hard wear surfaces or wall and ceiling covers. This task is accomplished by the combination of the actions indicated in claim 1. Further developments and improvements of the inventive idea are reflected in the characteristics of the dependent claims. If, in the present application, reference is made to footfall sound insulation, then by analogy, this is meant to include sound insulation as such when speaking of wall or ceiling covers.
When combining a thin sound-proofing layer that has positive effects with respect to the sound projection properties of rigid, acoustically stiff coverings, with a sound-attenuating layer that preferably is also relatively thin, and in particular consists of blister sheet filled with gas or air, one can take advantage of the sound-insulating benefits of double-shell designs while sticking to small design thicknesses which are particularly advantageous for renovations.
Air blister sheets are already known for footfall sound insulation beneath floating floor screeds, for instance from DE-A1-2841208 or CH-B-645968; however, with respect to room acoustics or aerial sound insulation, these proposals do not provide an adequate solution.
On the other hand, in contrast to technical sound-insulation precautions which are state of the art, such as an additional single layer like for instance the air blister sheet in the two documents cited above, or a sound-proofing layer according to DE-U1-29280016 consisting of cork and/or rubber chips bonded with polyurethane or of modified plaster of Paris, in the composite sound insulation system according to the invention, the two parameters chiefly influencing the sound projection properties of acoustically stiff wear surfaces, viz., inner sound attenuation and footfall sound improvement, which as such are known are now made optimizable for individual applications by the functional subdivision among several separate individual layers.
The materials of the first sound-proofing layer which is glued directly onto the bottom side of the wear surface should preferably have a density of more than 1600 kg/m3, which is a high value when considering materials for construction, and at the same time an inner loss factor xcex7int of 0.2 to 6.0. The attenuating layers contemplated in the composite sound insulation system according to the invention should advantageously attain masses per unit area of 10 kg/m2 or even less, depending on the layer thickness.
Apart from technical properties relating to thermal insulation and vapor diffusion, the composite sound insulation system according to the invention has three acoustic functions, viz.,
a) a precaution primarily concerning room acoustics, improving the sound projection properties of thin, rigid and acoustically stiff wear surfaces in the walking space, so as to avoid the rattling noise in the upper frequency range that is relevant to building acoustics, a noise which is typical for such floorings and extremely unpleasant subjectively.
b) a precaution to reduce footfall sound and achieve an acceptable footfall sound improvement factor even in the instance of acoustically stiff wear surfaces (as a variant of the softly resilient wear surfaces used most commonly to this effect in practical applications),
c) a precaution that in addition is effective as well with respect to aerial sound insulation.
The composite sound insulation system of the invention, by combining a thin, relatively light load distribution panel with a sound-proofing layer as well as with an air blister sheet of specific dimensions (which must have a dynamic stiffness not exceeding 20, and preferably not exceeding 10 MN/m3), extends the advantages of double-shell designs to flooring structures having relatively low masses per unit area of the individual layers. In specific cases, even a thin but sufficiently rigid wear surface can itself assume the load distribution function.
Starting from above or from inside (that is, always on the side of the room), the composite system according to the invention has the following individual components serving an overall optimization with respect to civil engineering physics of the desired double-shell floor screed layers or ceiling and wall coverings, that is, with respect to water vapor diffusion requirements (climate-dependent protection against humidity), footfall sound protection (sound projection into the room, sound conduction in solids to neighboring rooms) and a desirable, at least modest thermal insulation against heat dissipation or heat transfer:
if applicable, a vapor control or vapor seal (in a possible variant, taking the form of a flat sandwich heating element according to DE-A1-19823498, 19826544 or 19836148);
a sound-proofing layer with high inner loss factor xcex7int;
a footfall sound insulating layer with low dynamic stiffness sxe2x80x2, preferably consisting of blister sheets filled with gas or air.
In view of the fact that the wear surfaces and wall coverings which are intended to be acoustically improved by the composite system according to the invention may also be arranged directly above or in front of external structural components, it is recommended to apply a vapor control or vapor seal on the warm side of the composite system which will basically reduce or better inhibit the diffusion of water vapor to cold structural layers, thus preventing inadmissible condensate formation at the source and minimizing the fungus risk.
The sound-proofing layer has a favorable effect on the resonant frequency and degree of sound projection of single-shell floor and wall coverings which are thin but hard. In another variant, the sound-proofing layer can even be arranged as a top layer on the side of the room, for instance when it exists of polymeric glass which has a high inner loss factor xcex7int of about 0.6 combined with sufficient surface hardness and load distribution.
The dynamic stiffness sxe2x80x2 [MN/m3] of conventional footfall sound insulating products having a particular thickess which are commercially available results from a combination of dynamic stiffness of the matrix material and dynamic stiffness of the air present between this material. It is essential that with these products, the dynamic stiffness of the air in turn is strongly influenced by the fact that this air can escape along the borders of the conventional footfall sound-proofing panels. The present invention rests on the realization that functional footfall sound-proofing sheets, preferably suitable for rolling and in relatively small thicknesses between 5 and maximally 20 mm (preferably about 10 mm), can be produced and provide a dynamic stiffness of less than 10 MN/m3 when plastic blister sheet is used instead of e.g. fibrous insulating materials or fulled cellular plastic foams. In contrast to traditional air blister sheets which have become known from the packaging industry or for applications as insoles from U.S. Pat. No. 5,584,130, the gas or air-filled blisters of such footfall sound-proofing layers according to the invention which are intended for building applications are intentionally adjusted in their relative diameters, heights, and distances in such a way that the combination of matrix stiffness of the plastic sheet used, of dynamic stiffness of the gas (or air) enclosed in the blisters, and finally also of dynamic stiffness of the air present between the blisters when the sheet is installed, will result in a dynamic stiffness of less than 20, and preferably xe2x89xa610 MN/m3. This can be achieved, either already with a single-layer blister sheet or with a combination of two or more blister sheets.
In buildings, of course, the durability of footfall sound-proofing blister sheets will be a decisive practical factor in addition to its dynamic stiffness sxe2x80x2. To this end the thickness of the plastic sheets used must be so selected that the degree of filling of the blisters will be sufficiently constant over the relevant period of time, and the carrying capacity of the installed blister sheet will remain sufficiently large and stable.
The thermal protection that can be achieved with thin footfall sound-proofing blister sheets can be improved by lamination with top coatings if the side of these coatings facing the blisters has a high relative emission coefficient xcex5r (as close as possible to unity). This serves to minimize the fraction of global heat transfer due to heat radiation by the air layer present between blisters, the other fractions being due to convection and heat conduction.